1. Field of the Invention
The present invention relates to a vehicle periphery monitoring apparatus mounted to a vehicle such as a vehicle for picking up an image of a blind spot being out of the driver's visual field in the periphery of the vehicle.
2. Description of the Related Art
When a vehicle is approaching an intersection, it is necessary to confirm safe condition on left and right sides. However, at the intersection where the sight visibility on the left side and the right side is poor or where traffic lights are not equipped, the driver has to advance the vehicle into the intersection to some extent to confirm safe condition on the left side and the right side.
Therefore, care should be taken when advancing the vehicle into the intersection as described above, and after having entered therein, the driver has to view directly the left side and the right side respectively to confirm safe condition, which has been a mental burden for the driver.
Therefore, in these years, in order to alleviate the above-described burden, there is proposed a so-called vehicle periphery monitoring apparatus for supporting the driver by picking up the left and the right views on both sides of the vehicle by an image pickup device such as a CCD camera, which is mounted to a front grill or on a bumper of the vehicle, and displaying information on left and right images on both sides of the vehicle on a display device such as a LCD (liquid crystal display), which is installed in the interior of the vehicle (for example, see JP-A-2001-122020 and JP-A-2002-046531).
An apparatus disclosed in JP-A-2001-122020 has a differentiated configuration having a cover of an ideological form, such as characters, for covering the image pickup device. An apparatus disclosed in JP-A-2002-046531 has a configuration in which the design of the vehicle is preserved by providing an external cover for covering the distal end portion of the image pickup device.
According to the vehicle periphery monitoring apparatus as described above, since it is necessary to dispose an image pickup device such as the CCD camera, or an optical system equipment such as a reflection mirror or a prism for guiding outside views into the image pickup unit in a case, and thus a case configured of two halves is generally used.
For example, as shown in FIGS. 16 and 17, a case 1 includes a front case member 2 and a rear case member 3, and the front case member 2 and the rear case member 3 are adapted to be detachably secured with respect to each other by fastening screws 5 or the like with the intermediary of a packing 4.
In addition, in order to pick up left and right views, for example, the front case member 2 is provided with transparent transparent windows 2a for transmitting light beam on both sides thereof, and the portion other than the transparent windows 2a is light shielded by a color coating so as to prevent excessive light beam from coming into the interior of the case 1.
In this case, when employing the configuration in which the transparent windows 2a formed of transparent material and remaining portion of the front case member 2 formed of material having light shielding property are joined with respect to each other, water proof at the joint portion have to be taken into consideration.
Therefore, by forming the front case member 2 by itself of transparent resin material and coating the portion other than the transparent windows 2a with a color to secure the light shielding property, it is not necessary to take water proof at the portion around the transparent windows 2a into account. In this case, the color coating may be selected so as to match the member or the grill of the vehicle.
In this case, when applying the color coating material on the front case member 2, masking for preventing the coating from attaching to the transparent windows 2a is required. However, masking has a problem in that significant time and labor are required and thus cost increase is resulted.
In addition, it is necessary to apply a hardcoating material especially from the viewpoint of prevention of scratching on the transparent windows 2a. However, since the process of applying the hardcoating material is carried out after the color coating process, when defective application of the hardcoating material occurred in the downstream process, articles, which have been nondefectives in the upstream process, have to be scrapped. This results in yield loss and thus leads to increase in the cost.
In addition, since the coefficient of thermal expansion of the color coating material differs from that of the hardcoating material, cracking or peeling may be occurred in the coating material and the hardcoating material due to repetitive significant variations in temperature.
Furthermore, when scratches or cracks occurred on the front case member 2 during manufacture or after completion due to contact or collision of other member with the front case member 2 exposed toward the outside, the front case member 2 has to be replaced, and when it is secured by the screws 5, replacement will need significant time and labor.
Moreover, when a mating surface 6 between the front case member 2 and the rear case member 3 is directly exposed to high-pressure water during high-pressure washing of the vehicle, water might enter through a mating surface 6.